1. Field of the Invention
The present invention relates to a system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers and particularly, to a system for performing a soft hand-off between CDMA (Code Division Multiple Access) base transceiver stations under control of different CDMA base transceiver station controllers.
2. Description of the Prior Art
In a conventional CDMA system, a soft hand-off system is generally used for performing a hand-off between base transceiver stations (hereinafter, referred to as BTS) under the same base transceiver station controller (hereinafter, referred to as BSC). However, either of a hard hand-off system or a soft hand-off system which is performed under control of a mobile-services switching center (hereinafter, referred to as MSC) is used for performing a hand-off between BTSs under control of different BSCs because, as shown in FIG. 6, BSCs 1401, 1501 in the conventional CDMA system have no header converter and the conventional CDMA system has no link used for soft hand-off between BSCs.
The hard hand-off system adopts a method of deleting a current path before establishing a new path because the hard hand-off system is not capable of establishing a plurality of paths at the same time. Therefore, the hard hand-off system has a disadvantage of a short break which deteriorates a quality of communication.
On the other hand, the soft hand-off system adopts a method of deleting a current path after establishing a new path because the soft hand-off system is capable of establishing a plurality of paths at the same time. Therefore, the soft hand-off system does not have a disadvantage of the short break.
However, when performing a conventional soft hand-off between BTSs under control of different BSCs, the MSC has to perform both an information management and path controls (or call-in connection controls) for BSCs, BTSs, and MSs under control of the MSC. Therefore, the MSC is burdened with an excessive load, and moreover, a delay time of a communication becomes long. Thus, when performing the conventional soft hand off between BTSs under control of different BSCs, a communication quality deteriorates.
In order to overcome the aforementioned disadvantages, the present invention has been made and accordingly, has an object to provide a system for performing a soft hand off between base transceiver stations under control of different base transceiver station controllers which do not deteriorate a communication quality.
According to an aspect of the present invention, there is provided a system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers, the system comprising: a first base transceiver station of which a mobile station subjected to the soft hand-off is under control before the soft hand-off; a second base transceiver station of which the mobile station is under control after the soft hand-off; a first base transceiver station controller which controls the first base transceiver station; a second base transceiver station controller which controls the second base transceiver station; and a physical channel which connects the first base transceiver station controller with the second base transceiver station controller; wherein a first upstream data packet is transmitted from the mobile station to a codec in the first base transceiver station controller via the first base transceiver station; wherein a second upstream data packet is transmitted from the mobile station to the codec via the second base transceiver station, the second base transceiver station controller, and the physical channel; wherein a first downstream data packet is transmitted from the codec to the mobile station via the first base transceiver station; and wherein a second down stream data packet is transmitted from the codec to the mobile station via the physical channel, the second base transceiver station controller, and the second base transceiver station.
In the system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers, the first base transceiver station controller may comprise a header converter which converts a header of the second upstream data packet which has been used to bring the second upstream data packet toward the first base transceiver station controller to another header which is used to bring the second upstream data packet toward the codec.
In the system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers, the header of the second upstream data packet before the conversion may comprise: an identifier of an interface connected with the physical channel; an identifier of a switch port connected with the physical channel via the interface; and an identifier of the second base transceiver station controller.
In the system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers, the header converter may perform the conversion when the header converter determines that the second upstream data packet comes from a non-local base transceiver station controller on the basis of the identifier of the second base transceiver station controller.
In the system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers, the header of the second upstream data packet after the conversion may comprise: an identifier of the codec; and an identifier of a switch port which is connected with the codec.
In the system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers, the second base transceiver station controller may comprise a header converter which converts a header of the second downstream data packet which has been used to bring the second downstream data packet toward the second base transceiver station controller to another header which is used to bring the second downstream data packet toward the mobile station.
In the system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers, the header of the second downstream data packet before the conversion may comprise: an identifier of an interface connected with the physical channel; an identifier of a switch port connected with the physical channel via the interface; and an identifier of the first base transceiver station controller.
In the system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers, the header converter may perform the conversion when the header converter determines that the second downstream data packet comes from a non-local base transceiver station controller on the basis of the identifier of first base transceiver station controller.
In the system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers, the header of the second downstream data packet after the conversion may comprise: an identifier of an interface connected with the second base transceiver station; and an identifier of a switch port connected with the second base transceiver station via the interface.
In the system for performing a soft hand-off between base transceiver stations under control of different base transceiver station controllers, the header of the second downstream data packet after the conversion may further comprise an identifier of the second base transceiver station.
These and other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of the best mode embodiments thereof, as illustrated in the accompanying drawings.